Treatment of material containing iron



July 15, 1958 J. E. EBERHPIRDT 2,843,472

TREATMENT OF MATERIAL CONTAINING IRON Filed May 8, 1956 ORE PRE THE/l TER INVENTOR Q I John 5. Eberhard! ATTORNEY United States 2,843,472 TREATMENT'OF MATERIAL CONTAINING [RON John E. Eberhartlt, Bethlehem, Pa., assignor to Bethlehem Steel Company, a corporation of Pennsylvania Application May 8, 1956, Serial No. 583,473

10 Claims. (Cl. 75-1) This invention relates to the treatment of iron bearing ores and particularly ores which contain a substantial amount of oxygen as moisture and oxides.

it is especially useful in the beneficiation of iron bearing ores of the type containing oxides of metals other than iron such as the so-called Mayari type ores containing, besides iron, impurities such as chromium, nickel, cobalt, and manganese.

These ores are of a complex nature and are extremely difficult to break down into their various constituents.

The object of this invention is to separate the iron constituent from the remainder to make it suitable for use in steel making processes particularly in cases where the remaining constituents are undesirable.

The invention, in the main, is based on the use of hydrochloric acid gas and/or chlorine to produce ferric chloride according to the equations:

when energy in the form of heat is applied thereto thus to form ferric chloride vapor and water vapor and/or oxygen. Then the temperature of the vapors is increased according to the water vapor and/or oxygen content thereby to produce ferric oxide and hydrochloric acid gas and/or chlorine in accordance with the equations:

While in the broader aspects these facts are well known, nevertheless, the steps involved are very critical when applied to a commercial operation. I have discovered that in order to carry out an economical practice it is necessary to coordinate the oxygen content in the ores, as moisture and oxides, with the temperature at which the various steps in the process are carried out.

Mayari ores as they occur in nature contain considerable moisture and also a substantial amount of comdined water. Analyses of the ores vary considerably but in general they run within the ranges approximately as foliows, on a moisture and combined water free basis:

Percent Percent Fe 54 1.0 0.25 to 1.56

2. 2 2.0 to 2.7. 0.15 .0.05 to 0.35. 0. 5 0.24 to 1.70. 5. 0 116 to 8.0. 10. 0 6.0 to 14.0.

or to keep the system in balance.

My invention utilizes the fact that the boiling point of ferric chloride is considerably lower than the boiling points of the chlorides of most of the non-ferrous metals which are commonly associated with iron in iron ores. The approximate boiling point of ferric chloride is 607 F. Following is a list of the approximate boiling points of the chlorides of certain other metals found in various iron bearing ores:

Compound: Boiling point, F. CrCl 2312 CrCl 1760 Nlclg 1810 CoCl 1920 MnCl 2180 While the boiling points of aluminum chloride and silicon chloride are considerably lower than the boiling point of ferric chloride 1 have found that in my process the chlorine of the gases does not combine with the alumina and silica contents of the ore and they remain in the residue in their natural condition as they appear in the ore after the ores have been calcined and/ or somewhat reduced. Similarly I have found that in the case of Mayari ore the chlorine of the gases combines with the chromium content of the ore only to a limited extent.

1 will now describe examples of how my invention is put into practice particularly as it pertains to the treatment of Mayari' type ores.

Referring to the accompanying drawing, the finely divided Mayan ore in bin 11 is fed through conduits l2 and 13 into the ore pretreating chamber 14. A pretreating gas may be supplied to pretreater 14 through line 29 and exhausted therefrom through line 39. From this pretreating chamber the ore is fed through the conduits 15 and 16 into the chloridizing chamber 17 where the ore is subjected to the action of a hot gas consisting predominantly of hydrochloric acid which enters the bottom of the chamber through pipe 18. The temperature of the ore which enters this chloridizing chamber and the temperature of the gas which enters this chamer are such that the ore in the chloridizing chamber is maintained at about 1100 F. Under these conditions ferric chloride and water are formed, volatilized, and commingled with the gas. The gas, containing ferric chloride and water vapors, is drawn from the top of the chloridizing chamber through pipe 19 by means of pump 20, the gas then passing through pipe 21 to the gas reaction chamber 22. On its passage through pipe 21 the temperature of the gas may be increased by the gas heater 23 through which the pipe 21 passes. The increase in the temperature of the gas containing the vapors of water and ferric chloride causes the formation of ferric oxide, hydrochloric acid and chlorine. This reaction starts in pipe 21, at the location of the gas heater, but the principal amount of chemical change occurs in the reaction chamber 22. The ferric oxide produced is in the solid phase and drops into the lower part of the reaction chamber 22 and thus is separated from the gas. The greater part of the gas, now containing increased amounts of hydrochloric acid gas, then returns to the chloridizing chamber through the closed system indicated on the drawing. The system is started and replenished by entering appropriate gas or gases through pipe 18. The other solid constituents of the ore plus unvaporized chlorides of other metals present leave chamber 17 through pipe 26. Bleed-off valve 27 may be used if needed to vent the system of impurities Solid ferric oxide leaves reaction chamber 22 through pipe 28.

It is understood that with the above treatment nickel, cobalt and manganese are formed into chlorides. However, the temperature of the chloridizing chamber is well below the boiling points of these chlorides so that only exceedingly small amounts of the chlorides of these other metals, which are hereinafter referred to in the description and claims as the nickel group metals, will be volatilized and by far the greater part will remain with the gangue.

In my preferred form 'of process I contact the solid materials intimately with the gases by the fluidized technique, that is the finely divided solid materials are held in suspension. However, my invention is not limited to the use of this technique and can be applied to a bed of solid material which is not in suspension.

My invention is not in any way limited to the practice of beneficiating Mayari ores and it can be successfully used when treating other kinds of ores containing oxides of iron. I have illustrated my invention in the practice of beneficiating Mayari ores for the reason that particular care should be taken so as not to produce an excess of water vapor in the system as water is formed from the reaction of the nickel group metal oxides, in the chloridizing chamber, in addition to the water formed during the chloridizing of the ferric oxide. Generally the quantity of water formed in the chloridizing chamber, due to the chloridizing of ferric oxide, is substantially eliminated by the reverse reaction in the reaction chamber, but the quantity of water due to the chloridization of the nickel group metal oxides is too voluminous to be eliminated in the reaction chamber, in view of the fact that the nickel group metal chlorides are not volatilized and therefore do not enter the reaction chamber 22 to take part in the reverse reaction to form hydrochloric acid and thereby get rid of the water. Therefore, the water content of the circulating gas would continue to build up unless something were done to reduce it.

Accordingly in treating Mayari type ores, I can bleed off a portion of the gas which issues from the reaction chamber 22 and remove water therefrom after which I may return the gas to the circuit. Moreover, I can add additional chlorine containing gas to compensate for the loss of chlorine due to the formation of nickel group metal chlorides. However, my preferred and more economical method would be to treat the ores in the pretreating chamber 14 in such manner that the oxygen content of the ore in the form of Water and oxide is controlled so as not to burden the system with an excessive amount of water vapor in the subsequent steps of the operation. Furthermore, in the case of ores containing large amounts of metals other than iron, such as Mayari type ores, I find it very beneficial to reduce somewhat the oxides contained in the ore by means of a reducing medium such as hydrogen or coal introduced into the pretreating chamber. In this case the amount of reduction taking place during the pretreatment of V the ore should preferably consist of the removal of at least an amount of oxygen equivalent to the complete reduction to the metallic state of the oxides of the nickel group metals. The closed gas cycle can then be brought into complete balance by adding chlorine gas and/or hydrochloric acid gas to the gases entering the chloridizing chamber and, if necessary, by adding steam and/or oxygen gas to the gases entering the reaction vessel chamber. The amount of oxygen to be added in the reaction chamber will depend upon the state of the pretreated ore entering the chloridizing chamber. It should be in any event be sufiicient to keep the recirculating gas stream in balance, that is, sufficient to prevent any depletion of oxygen resulting from formation of ferric oxide from ferric chloride made initially from pretreated ore containing lower oxides of iron. Ideally, the amount of oxygen addedshould not be greater than the amount required to effect complete conversion of ferric chloride to ferric oxide. From the foregoing explanation it will be readily apparent to one skilled in the art that adding proper combinations of the four gases mentioned, together with the reversible reaction which occurs in the recirculating stream of gases, will supply the chlorine leaving the system as nickel and other chlorides, will supply any oxygen needed to assure complete conversion of ferric chloride to ferric oxide, and will maintain the balance among the constituents of the recirculating stream of gases without removal of any water vapor from said stream.

Referring further to the drawing, the oxygen to be added to the system may be supplied to pipe 21 through line 24. Chlorine required for making up the chlorine lost in the form of the nickel group metal chlorides may be supplied to pipe 18 through line 25.

Under these conditions I have discovered that I get a very satisfactory result if I maintain the ore in the chloridizing chamber at a temperature between 610 F. and 1100 F. and that the amount by which I must raise the temperature of the gases in the reaction chamber to produce a satisfactory conversion of ferric chloride to ferric oxide is dependent on the amount of reduction of the ore during pretreatment, the more reduction during pretreatment, the more oxygen must be added, and the less the amount by which the temperature must be increased. In the case of reduction during pretreatment corresponding to removal of only an amount of oxygen corresponding to reduction of the nickel group metal oxides to the metallic state, I find that an increase in temperature of F. results in a satisfactory conversion of ferric chloride to ferric oxide. In practice I prefer to increase the temperature by a greater amount up to the practical limit to increase the conversion; still further increases inconversion can be obtained through a greater degree of reduction during pretreatment corresponding to greater additions of oxygen into the re action vessel. The optimum temperature in the reaction chamber is in a range between about 950 F. and 1700 F. and about 100 F. or more higher than the temperature in the chloridizing chamber. Under certain circumstances I find that the ferric chloride vapor is not converted completely to solid ferric oxide but part of it is carried over with the gases that are recycled back to the chloridizing chamber.

-While I find that hydrochloric acid gas is preferable to chlorine gas as the main chloridizing agent, I sometimes desire to use some chlorine gas with the hydrochloric acid gas. When hydrochloric acid gas alone is used not only is ferric chloride formed but also some ferrous chloride may be formed. This is a disadvantage as the formation of ferrous chloride is inclined to prevent an effective separation of iron from the other ore constituents as would otherwise be possible if only ferric chloride were formed. The reason for this will be apparent when one considers the relative boiling points of ferrous and ferri chlorides. While ferric chloride has the relatively low boiling point of about 607 F., ferrous chloride has the relatively high boiling point of about 1880 F. Now consider what would happen if one were treating iron ores containing nickel, such as the Mayari type ores mentioned above, with the chloridizing gas consisting solely of hydrochloric acid gas. The temperature for chloridizing would be not less than the boiling point of ferric chloride but it would be less than the boiling point of nickel chloride. Under these conditions the ferric chloride formed would be volatilized and removed from the ore but the ferrous chloride formed would remain with the nickel in the ore.

When hydrochloric acid gas is used alone, the amount of ferrous chloride formed is not nearly as great as the amount of ferric chloride, but usually I desire to inhibit the formation of substantial amounts of ferrous chloride. This I do by the use of some chlorine with the hydrochloric acid gas. In my preferred practice I employ hydrochloric acid gas in predominant amount but with enough chlorine to substantially inhibit the formation of ferrous chloride. The amount of chlorine to use with the hydrochloric acid will vary with varying conditions but usually the amount will be from to by volume of the chloridizing gas.

While the foregoing description has been directed mainly to the details of treating Mayari type ores, the process may advantageously be employed in the treatment of other ores containing iron such as taconite. The partial re duction of the iron oxide as a pretreatment, with subsequent replacement of the required amount of oxygen in the reaction chamber results in greater conversion of the ferric chloride vapor to ferric oxide. In the treatment of such ores, the desired degree of preliminary reduction can not be given here as a definite fiigure, but will depend mainly on economic considerations.

My process is applicable to the treatment of oxidic materials, i. e. materials containing oxides or compounds which during the chloridizing reaction react as do the oxides to form ferric chloride and an oxidizing gas. If the material to be treated is not oxidic, as, for example, a sulfide ore, it should be roasted to the oxide state before treatment by my process.

As used herein, hydrochlori acid means either bydrochloric acid gas alone or mixed with chlorine, and chlorine means either chlorine gas alone or mixed with hydrochloric acid. Oxygen may mean steam, other gaseous oxides or simply oxygen alone.

I claim:

1. In a process for treating an ore bed containing ferric oxide and non-ferric oxides capableof being chloridized, the steps of reducing said oxides a predetermined amount, chloridizing the bed at a temperature to change the oxides to chlorides and to form vaporized ferric chloride and water vapor, the amount of oxides reduced before chloridizing being at least stoichiometrically equivalent to the amount of chlorine combining in the chloridizing step with the nickel group metals, removing said ferri chloride vapor and said water vapor from the environment of said bed, forming a gaseous body comprising said ferric chloride vapor and water vapor in a predetermined ratio of ferric chloride vapor to Water vapor, the oxygen content of said water vapor being at least sufficient to convert said ferric chloride to ferric oxide, and heating the gaseous body to a temperature from 950 F. to 1700 F. to an amount depending upon said ratio thereby to change most of the ferric chloride vapor to solid ferric oxide and most of the water vapor to hydrochloric acid gas, said temperature being varied inversely with the amount of reduction before chloridizing.

2. In a process for treating a bed of ore containing ferric oxide and non-ferric oxides capable of being chloridized, the steps of reducing said oxides a predetermined amount, chloridizing the bed at a temperature to change the oxides to chlorides and to form ferric chloride vapor and water vapor, the amount of oxides reduced before chloridizing being at least stoichiometrically equivalent to the amount of chlorine combining in the chloridizing step with the nickel group metals, removing the vapors thus formed from the environment of the bed, forming a gaseous body comprising said ferric chloride vapor and oxygen in a predetermined ratio of ferric chloride vapor to oxygen, the amount of oxygen being at least suflicient to convert said ferric chloride to ferric oxide, and heating the body to a temperature at which substantially all of said body is changed to solid ferric oxide and a gas containing chlorine.

3. In a process for treating a bed of ore containing iron, the steps of pretreating the ore and controlling the oxygen present as moisture and oxides, treating the ore in a chamber containing chlorine at a temperature to form ferric chloride vapor and water vapor, removing the ferric chloride vapor and water vapor to a second chamber, forming a gaseous body comprising ferric chloride and oxygen in a predetermined ratio, the amount of oxygen being at least sufiicient to convert said ferric chloride to ferric oxide, raising the temperature of the gaseous body at least F. but not higher than 1700 F. thereby to form a solid containing iron and a gas containing chlorine, and returning at least a portion of the gas thus formed to the first chamber.

4. In a process for treating an ore containing iron, the steps of preparing the ore body so that there is a predetermined amount of oxygen present as moisture and oxides, the amount of oxygen present in said ore body after so preparing it being less than the amount capable of combining stoichiometrically with the metals present in said ore body, forming in a first chamber a fluidized bed of the ore in an atmosphere containing hydrochloric acid gas at a temperature to fonn a gaseous mass comprising ferric chloride vapor and Water vapor, removing said gaseous mass from the environment of the bed to a second chamber, heating said gaseous mass in the second chamber at a temperature predetermined by the amount of oxygen in said body, after the preparing step and prior to its entrance into said fluidized bed thereby to convert a substantial part of said mass to ferric oxide and hydrochloric acid gas, removing the latter gas from the second chamber, and returning at least a portion thereof to the first chamber.

5. In a process for treating an ore containing ferric oxide, the steps of pretreating the ore to control the oxygen present as moisture and oxides, forming in a first chamber a heated bed of the treated ore fluidized with a gas containing chlorine in sufficient quantity to convert a substantial part of the ferric oxide to ferric chloride vapor and water vapor while limiting the temperature to a point not substantially above 1100 F., removing the ferric chloride vapor and the water vapor from the environment of said bed to a second chamber remote from said bed, forming a gaseous body comprising said ferric chloride vapor, said water vapor, and an additional gas containing oxygen so that a predetermined ratio exists between the ferric chloride and the oxygen, the total amount of oxygen being at least suflicient to convert said ferric chloride to ferric oxide, and raising the temperature of the vapors in the gaseous body to convert at least a portion of the vapors to an iron containing solid.

6. In a process for treating a bed of ore containing iron, the steps of pretreating the ore to control the oxygen present as moisture and oxides, treating the ore in a chamber containing hydrochloric acid gas at a temperature to form ferric chloride vapor and water vapor, forming a gaseous body including said vapors and additional oxygen at a point remote from the ore bed at a temperature depending upon the ratio of the ferric chloride vapor to oxygen and sufiiciently high to change a substantial portion of said body to a solid containing iron and a gas containing chlorine, the total amount of oxygen present in said gaseous body being at least sufficient to convert said ferric chloride to ferric oxide, and varying the temperature inversely with the amount of additional oxygen supplied to said gaseous body.

7. In a process for treating Mayari ore, the steps of pretreating the ore and controlling the oxygen present as moisture and oxides, the amount of oxygen present after pretreating the ore being no greater than the amount capable of combining stoichiometrically with the metals other than nickel group metals present in the ore, treating the ore in a chamber containing a chlorine gas at a temperature to form ferric chloride vapor and water vapor, treating said vapor at a point remote from the ore bed at a temperature depending upon the oxygen present in said vapor and sufl'iciently high to change a substantial portion of vapors to a solid containing iron and a gas containing chlorine.

8. A process of treating Mayari type ores for the recovery of iron therefrom comprising pretreating a body of such ore under reducing conditions to remove therefrom an amount of oxygen at least equal to that corresponding to complete reduction to the metallic state of the oxides of the nickel-group metals, removing ore from said pretreated body to a chloridizing chamber and there subjecting said ore to the action of a gas including hydrochloric acid gas While said ore is at a temperature above the boiling point of ferric chloride but below the boiling point of any chloride of the nickel-group metals to form a gaseous mixture including ferric chloride vapor and water vapor resulting from reaction of part of said hydrochloric acid gas with said pretreated ore, removing the solid residue remaining after said reaction and removing said gaseous mixture to a reaction chamber, elevating the temperature of said mixture, and adding thereto an amount of oxygen dependent upon the amount removed during said pretreatment to effect conversion of part of said ferric chloride vapor to solid ferric oxide, hydro-- chloric acid gas, and chlorine, removing the ferric oxide so formed from the reaction chamber, and returning the gases formed in said conversion together with any unreacted gases having entered the reaction chamber to the chloridizing chamber.

9. A process of treating Mayari type ores containing iron oxide for the recovery of iron therefrom comprising pretreating a body of such ore under reducing conditions to remove therefrom an amount of oxygen at least equal to that corresponding to complete reduction to the metallic state of the oxides of the nickel-group metals, removing ore from said pretreated body to a chloridizing chamher and there subjecting said ore to the action of a gas including hydrochloric acid gas while said ore is at a temperature above the boiling point of ferric chloride but below the boiling point of any chloride of the nickelgroup metals to form a gaseous mixture including ferric chloride vapor and water vapor resulting from reaction of part of said hydrochloric acid gas with said pretreated ore, removing the solid residue remaining after said reaction and removing said gaseous mixture to a reaction chamber, elevating the temperature of said mixture, and adding thereto an amount of oxygen substantially equal to the amount of oxygen removed from the iron oxide during said pretreatment to effect conversion of part of said ferric chloride vapor to solid ferric oxide, hydrochloric acid gas, and chlorine, removing the ferric oxide so formed from the reaction chamber, and returning the gases formed in said conversion together with any unreacted gases having entered the reaction chamber to the chloridizing chamber.

10. In a process for treating a bed of ore containing iron, the steps of pretreating the ore and controlling the oxygen present as moisture and oxides, treating the ore in a chamber containing chlorine at a temperature to form ferric chloride vapor and Water vapor, removing the ferric chloride vapor and Water vapor to a second chamher, forming a gaseous body comprising ferric chloride and oxygen in a predetermined ratio, the amount of oxygen in said gaseous body being at least sufficient to convert said ferric chloride to ferric oxide, raising the temperature of the gaseous body at least 100 F. but not higher than 1700 F. thereby to form a solid containing iron and a gas containing hydrogen and chlorine, and returning at least a portion of the gas thus formed to the first chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,916,853 Wescott July 4, 1933 1,928,406 Bacon et a1. Sept. 26, 1933 2,030,867 Hart Feb. 18, 1936 2,291,206 Bowes July 28, 1942 

1. IN A PROCESS FOR TREATING AN ORE BED CONTAINING FERRIC OXIDE AND NON-FERRIC OXIDES CAPABLE OF BEING CHLORIDIZED, THE STEPS OF REDUCING SAID OXIDES A PREDETERMINED AMOUNT, CHLORIDIZING THE BED AT A TEMPERATURE OF CHANGE THE OXIDES TO CHLORIDES AND TO FORM VAPORIZED FERRIC CHLORIDE AND WATER VAPOR, THE AMOUNT OF OXIDES REDUCED BEFORE CHLORIDIZING BEING AT LEAST STOICHIOMETRICALLY EQUIVALENT TO THE AMOUNT OF CHLORINE COMBINING IN THE CHLORIDIZING STEP WITH THE NICKEL GROUP METALS, REMOVING SAID FERRIC CHLORIDE VAPOR AND SAID WATER VAPOR FROM THE ENVIRONMENT OF SAID BED, FORMING A GASEOUS BODY COMPRISING SAID FERRIC CHLORIDE VAPOR AND WATER VAPOR IN A PREDETERMINED RATIO OF FERRIC CHLORIDE VAPOR TO WATER VAPOR, THE OXYGEN CONTENT OF SAID WATER VAPOR BEING AT LEAST SUFFICIENT TO CONVERT SAID FERRIC CHLORIDE TO FERRIC OXIDE, AND HEATING THE GASEOUS BODY TO A TEMPERATURE FROM 950*F. TO 1700*F. TO AN AMOUNT DEPENDING UPON SAID RATIO THEREBY TO CHANGE MOST OF THE FERRIC CHLORIDE VAPOR TO SOLID FERRIC OXIDE AND MOST OF THE WATER VAPOR TO HYDROCHLORIC ACID GAS, SAID TEMPERATURE BEING VARIED INVERSELY WITH THE AMOUNT OF REDUCTION BEFORE CHLORIDIZING. 